The glass is much better in the 2 vs the 1. Resolution, light transmission, and it's ED vs non on the 1. The turret design is quite a bit different. They're lower profile which is nice. The zero stop is a completely different design and has the updated Revlimiter design that takes about 2 seconds to set. XRS II has EXO Barrier, I can't remember if the gen 1 has Rainguard even. XRS II has the Throw Hammer, which is awesome. XRS II = locking diopter.
Those are the main things that come to mind.